Intersection

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题目

Implement the type version of Lodash.intersection with a little difference. Intersection<T> takes an Array T containing several arrays or any type element including the union type, and returns a new union containing all intersection elements.

type Res = Intersection<[[1, 2], [2, 3], [2, 2]]>; // expected to be 2
type Res1 = Intersection<[[1, 2, 3], [2, 3, 4], [2, 2, 3]]>; // expected to be 2 | 3
type Res2 = Intersection<[[1, 2], [3, 4], [5, 6]]>; // expected to be never
type Res3 = Intersection<[[1, 2, 3], [2, 3, 4], 3]>; // expected to be 3
type Res4 = Intersection<[[1, 2, 3], 2 | 3 | 4, 2 | 3]>; // expected to be 2 | 3
type Res5 = Intersection<[[1, 2, 3], 2, 3]>; // expected to be never

解答

type Intersection<T> = T extends [infer First, ...infer Rest]
  ? (First extends unknown[] ? First[number] : First) & Intersection<Rest>
  : unknown;